The present invention relates to a device for controlling engine valves, and more specifically relates to a controller for varying the valve operating characteristics of intake valves and exhaust valves of an internal combustion engine.
An example of a conventional controller for controlling the valve timing of engine valves is disclosed in Japanese Laid-Open Patent Publication No. 2001-55935. This controller is provided with a variable mechanism for varying the valve timing by changing the relative rotation phase of a camshaft, and a lock mechanism for locking the relative rotation of the camshaft when the relative rotation phase is at a predetermined lock phase. In this controller, the change in the relative rotation phase, that is, the varying of the valve timing, is possible by unlocking the relative rotation of the camshaft. This controller is further provided with a means for detecting the unlocking of the relative rotation of the camshaft. When the unlocking is detected by the detecting means, the controller provides feedback control of the relative rotation phase such that the relative rotation phase approaches a target relative rotation phase.
When such a valve timing controller is applied to an internal combustion engine having a plurality of cylinder groups as in the case of V-type engines, each cylinder group is generally provided with a separate variable mechanism and lock mechanism. In this structure, it is desirable that the relative rotation phases be equal in all variable mechanisms. This arrangement is used because when a difference occurs in the relative rotation phases among the variable mechanisms, a change in torque is generated due to the torque difference among the cylinder groups.
When an unlocking operation is not performed properly in one of the lock mechanisms, however, the relative phase rotation of the camshaft is not properly unlocked. The relative rotation phase is maintained in the lock phase in the variable mechanism corresponding to the lock mechanism which cannot unlock the relative rotation of the camshaft. The previously mentioned feedback control is performed in the other variable mechanism corresponding to the lock mechanisms which unlocks the relative rotation of the camshaft. That is, the relative rotation phase is only changed to the target rotation phase in the other variable mechanism. As a result, a difference in the relative rotation phases is generated between the variable mechanism that does not unlock the relative rotation and the variable mechanism that unlocks the relative rotation, and a change in torque is generated in conjunction with this condition.